Many manufacturing processes produce a large quantity of waste material.
For example, machining materials typically produces large quantities of waste material in the form of swarf, such as the waste metal shavings produced when milling a metal block. The swarf tends to be contaminated with cutting fluid, lubricant, cooling fluid, grease or any other product that was used during the machining process.
As another example, millscale, an iron oxide residue left on the surface of hot rolled steel which must be removed before the steel can be used, is a waste material produced in large quantities in steel manufacture. The millscale tends to become contaminated with oil, grease and other contaminants used during the removal of the millscale or the processing of the steel.
There are economic and environmental motivations for trying to recycle waste material into new material for reuse. The economic motivations include the facts that many materials, particularly metals, are expensive so dumping waste material is wasting a potentially valuable resource, and there are also significant costs involved in waste disposal. The environmental motivations include the facts that dumping the waste material is a waste of limited resources, unnecessarily fills waste disposal sites and leads to potential pollution from both the waste material and the contaminants. Dumping waste material also means that it is necessary to extract further new material with an associated environmental impact involved in extracting new material.
Before recycling waste material into new material, it is necessary to remove contaminants from the waste material to prevent the contaminants from contaminating the new material. However, it is difficult to remove contaminants from waste material.
Existing method of cleaning contaminants from waste material use detergents (which are inefficient), organic solvents such as trichloroethylene (which are toxic, environmentally unfriendly, and whose use is heavily legally regulated), or heat (which is expensive because of the large quantities of fuel, such as gas, required).
Despite the economic and environmental benefits to recycling waste material, there is currently no cost effective, reliable and environmentally friendly way of removing contaminants from waste material which means that most waste material is dumped rather than recycled.
It is therefore desirable to find a cost effective, reliable and environmentally friendly way to remove contaminants from waste material.